Although, until today I didn't even have Klingon Border.
Previously I played with another opponent who bought everything, so instead I just tended to buy booster packs for my chosen races to supplement the SSDs he already had. But I don't play with him anymore so today I picked up Klingon Border, Romulan Space and Reinforcements Attack.
As for reinforcements attack, some comments:
1. Personally it was not my first choice. I would have rather bought Distant Kingdoms, or perhaps Klingon Attack or one of the other supplements already focused on my race. But it was a better choice than transports attack so I grabbed it.
2. I had a look at the thing and I'm not a huge fan but I don't hate it either. what I would say is that in general I prefer products that focus on specific races.
When I buy boosters for example, I MUCH prefer the booster that have the most ships for a specific faction. So I prefer a booster like #11 with nothing but Gorn, over a booster like #9 which is Gorn and Romulan.
So yeah Reinforcements Attack is the complete opposite of what i prefer in terms of mix.
And some of the ships included are a bit weird, "Destroyer-Battlecruiser" or whatnot for example, but in terms of stats they're probably okay. They just include ships for a lot of factions I haven't yet bought into yet.